Add more linters to improve code readability (#19989)

Add nakedret, unconvert, wastedassign, stylecheck and nolintlint linters to improve code readability

- nakedret - https://github.com/alexkohler/nakedret - nakedret is a Go static analysis tool to find naked returns in functions greater than a specified function length.
- unconvert - https://github.com/mdempsky/unconvert - Remove unnecessary type conversions
- wastedassign - https://github.com/sanposhiho/wastedassign -  wastedassign finds wasted assignment statements.
- notlintlint -  Reports ill-formed or insufficient nolint directives
- stylecheck - https://staticcheck.io/docs/checks/#ST - keep style consistent
  - excluded: [ST1003 - Poorly chosen identifier](https://staticcheck.io/docs/checks/#ST1003) and [ST1005 - Incorrectly formatted error string](https://staticcheck.io/docs/checks/#ST1005)

modules/highlight/highlight.go

@@ -114,7 +114,7 @@ func CodeFromLexer(lexer chroma.Lexer, code string) string {
 	htmlbuf := bytes.Buffer{}
 	htmlw := bufio.NewWriter(&htmlbuf)
 
-	iterator, err := lexer.Tokenise(nil, string(code))
+	iterator, err := lexer.Tokenise(nil, code)
 	if err != nil {
 		log.Error("Can't tokenize code: %v", err)
 		return code
@@ -197,7 +197,7 @@ func File(numLines int, fileName, language string, code []byte) []string {
 
 	m := make([]string, 0, numLines)
 	for _, v := range strings.SplitN(htmlbuf.String(), "\n", numLines) {
-		content := string(v)
+		content := v
 		// need to keep lines that are only \n so copy/paste works properly in browser
 		if content == "" {
 			content = "\n"
@@ -220,8 +220,8 @@ func File(numLines int, fileName, language string, code []byte) []string {
 // return unhiglighted map
 func plainText(code string, numLines int) []string {
 	m := make([]string, 0, numLines)
-	for _, v := range strings.SplitN(string(code), "\n", numLines) {
-		content := string(v)
+	for _, v := range strings.SplitN(code, "\n", numLines) {
+		content := v
 		// need to keep lines that are only \n so copy/paste works properly in browser
 		if content == "" {
 			content = "\n"